Changes in sources of shared variability of body size and shape in Egyptian local and New Zealand White breeds of rabbits during growth

Abstract. Correlations between body weight and measurements (body length, thigh circumference, shank length and chest width) at 6, 8, 10 and 12 weeks of age in New Zealand White (NZW), Red Baladi (RB), Black Baladi (BB) breeds of rabbits were studied by factor analysis to disclose the main sources of shared variability, to deduce the factors that describe these characteristics and to quantify breed differences in morphometric size and shape variation during growth.

Differences and similarities between NZW and Egyptian rabbit breeds in factors describing variations in size and shape characters are discussed. At marketing age, compared with local breeds (RB and BB), NZW had higher communality (proportion of variance for a variable that is shared in common by other variables) for chest width and lower communality for body weight and other body shape characters. Compared with NZW, Egyptian breeds varied more in size and less in shape characters. Finding indicated that most of the common variability in live performance traits could be accounted for by two factors with the influence of general factor preponderating. Irrespective of breed, the first factor at various ages was interpreted as a general size factor. The second factor varies with breed and stage of development. In NZW, this factor at all ages (6 to 12 weeks) was described as chest width factor. The second factor in RB was designated to chest width (at 6 and 8 weeks) and a shank length at 10 and 12 weeks. In BB, the second factor was designated to chest width (at 6 weeks), a shank length (at 8 and 10 weeks) and to thigh circumference (at 12 weeks). The importance of the general size factor in relation to the second factor (shape) changes with age. The contribution of the general size factor to the total variance decreased with age in both NZW and RB, but it showed irregular pattern in BB. While that of the second factor increased with advancing age from 6 to 12 weeks in RB and from 6 to 10 weeks in NZW.